As an assembly for use in applications such as a catalyst converter for use in a chemical reaction apparatus using exhaust gas purification and catalyst functions of an internal combustion engine, a filter, and a heat exchanger, an assembly has been known in which a material of compressive elasticity having a cushioning property is disposed between a cell structure and a cylindrical metal container (can member) and a predetermined compressive surface pressure is applied to the cell structure via the material of compressive elasticity to accommodate and hold (canning) the cell structure in the metal container.
For example, when the assembly is used as the catalyst converter for purifying a car exhaust gas, noble metals such as platinum, palladium, and rhodium are dispersed and loaded as a catalyst component in a ceramic honeycomb structure as one type of the cell structures, and this structure is accommodated and held in the metal container (can member) via a ceramic mat and mounted in an exhaust system.
At this time, when the catalyst components are loaded in the cell structure as described above, a loading amount changes with a weight of the structure. However, in order to control this loading amount, it is necessary to correctly manage the weight of the cell structure in a loading process.
Moreover, the cell structure needs to be accommodated and held in the metal container in an appropriate state. However, since an outer shape dimension of the cell structure is correctly managed in the canning process, even a ceramic honeycomb structure having a large dimensional fluctuation after firing can practically be used without machining/processing an outer periphery of the structure.
Furthermore, the steps for manufacturing, loading, canning, and the like can be traced back and recognized, by checking the lot number of the cell structure marketed after having been mounted in a car.
Therefore, for the cell structure, as shown in FIG. 2, an outer wall 4 has been marked with useful information 10 such as the weight, dimension, characteristics, lot number, and manufacturing conditions.
The information 10 is practically used for smooth and efficient operation of the production line, by reading it visually or mechanically by the users.
When the catalyst is loaded, in general, the catalyst components are not loaded by the outer wall of the honeycomb structure, and therefore the marked displayed information is not buried in the catalyst components. However, when the catalyst is loaded by applying it to the through channels in the cell structure, a solution containing a catalyst exudes to the outer wall of the cell structure by a capillary phenomenon through pores connected to one another, and an information displayed portion on an outer wall surface is also colored. In this case, the information is not easily read. When the information is not uniformly colored or colored in a spotted manner, there is a problem that the information cannot be read in a mechanical read method requiring clearness as in image analysis.
To solve the problem, marking ink has been selected so that the developed color of the displayed information obtains a sufficient contrast with respect to the catalyst solution. However, the information is colored mainly in various brownish colors from dark brown to black in accordance with types or concentrations of the catalyst components. Therefore, it is difficult to handle all the catalyst solutions, and this has been a factor for inhibiting automation of the marking.
The present invention has been developed in consideration of the above-described conventional problems, and an object is to provide a method for protecting displayed information, on which a displayed information portion is prevented from being colored after loading catalyst components and the displayed information can be maintained in a readable state, and a cell structure of which the surface information is protected by the protection method.